Evolution of HCN by thermal oxidative degradation from nylon 66 at high temperatures including burning

Work on the evolution of HCN from nylon 66 was extended to temperatures from ca. 300 to 695°C. Below ca. 300°C the evolution of HCN is governed by chemical decomposition, and above 300°C the evolution is controlled by diffusion. Above 530°C oxidation of HCN becomes noticeable and ignition occurs at 590°C. The rate constants for all of the temperature ranges and for the oxidation of HCN are given in terms of Arrhenius equations. The activation energy for the oxidation of HCN before ignition (590°C) is reached is 47 kcal/mole, and beyond this point, the oxidation is controlled by diffusion. The rate constants increase linearly with oxygen concentration as long as HCN oxidation is negligible; however, they pass through maxima if HCN oxidation is appreciable (some HCN is evolved even in the absence of oxygen). A new flash degradation apparatus has been constructed for these high-temperature ranges and a degradation mechanism has been proposed which is in satisfactory agreement with the experimental results.